/*
This file is part of Lproxy.

Lproxy is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Lproxy is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Lproxy.  If not, see <http://www.gnu.org/licenses/>.
*/
package lproxy_client;

class Base64Converter {
private Base64Converter(){}
private static char[] map1 = new char[64];
static
{
        int i=0;
        for (char c='A'; c<='Z'; c++) map1[i++] = c;
        for (char c='a'; c<='z'; c++) map1[i++] = c;
        for (char c='0'; c<='9'; c++) map1[i++] = c;
        map1[i++] = '+'; map1[i++] = '/';
}
private static byte[] map2 = new byte[128];
static
{
        for (int i=0; i<map2.length; i++)
                map2[i] = -1;
        for (int i=0; i<64; i++)
                map2[map1[i]] = (byte)i;
}
public static String encode (String s)
{
        return new String(encode(s.getBytes()));
}

public static char[] encode (byte[] in)
{
        int iLen = in.length;
        int oDataLen = (iLen*4+2)/3; 
        int oLen = ((iLen+2)/3)*4;
        char[] out = new char[oLen];
        int ip = 0;
        int op = 0;
        while(ip < iLen)
        {
                int i0 = in[ip++] & 0xff;
                int i1 = ip < iLen ? in[ip++] & 0xff : 0;
                int i2 = ip < iLen ? in[ip++] & 0xff : 0;
                int o0 = i0 >>> 2;
                int o1 = ((i0 & 3) << 4) | (i1 >>> 4);
                int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
                int o3 = i2 & 0x3F;
                out[op++] = map1[o0];
                out[op++] = map1[o1];
                out[op] = op < oDataLen ? map1[o2] : '='; op++;
                out[op] = op < oDataLen ? map1[o3] : '='; op++;
        }
        return out;
}

public static byte[] decode (String s) throws Exception
{
        char[] in = s.toCharArray();
        int iLen = in.length;
        if(iLen%4 != 0)
                throw new Exception("Length of Base64 encoded input string is not a multiple of 4.");
        while(iLen > 0 && in[iLen-1] == '=')
                iLen--;
        int oLen = (iLen*3) / 4;
        byte[] out = new byte[oLen];
        int ip = 0;
        int op = 0;
        while(ip < iLen)
        {
                int i0 = in[ip++];
                int i1 = in[ip++];
                int i2 = ip < iLen ? in[ip++] : 'A';
                int i3 = ip < iLen ? in[ip++] : 'A';
                if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127)
                        throw new Exception("Illegal character in Base64 encoded data.");
                int b0 = map2[i0];
                int b1 = map2[i1];
                int b2 = map2[i2];
                int b3 = map2[i3];
                if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0)
                        throw new Exception("Illegal character in Base64 encoded data.");
                int o0 = ( b0 <<2) | (b1>>>4);
                int o1 = ((b1 & 0xf)<<4) | (b2>>>2);
                int o2 = ((b2 & 3)<<6) | b3;
                out[op++] = (byte)o0;
                if (op<oLen)
                        out[op++] = (byte)o1;
                if (op<oLen)
                        out[op++] = (byte)o2;
        }
        return out;
}
}
